Progressively deeper coal seams with higher rock temperatures are mined in order to achieve higher outputs in coal mines.  This fact, and the heat arising out of underground work with machines with high engine power, mean that ventilation and acclimatisation of mines are in high demand. The mining areas require large air quantities for cooling and gas thinning. Effective air conditioning systems are a prerequisite to mining in deep mines with high rock temperatures.

To achieve this, refrigerating plants have been installed above ground. These cool the coolant water with chiller units and transport it underground through shaft pipes with diameters up to 400 mm. Due to the large height differences involved, high hydrostatic pressure builds up in the shaft pipes. In order to link the cold-water circuit with the secondary underground water circuit, a so-called pressure exchange system is installed, which reduces the pressure to about 30 bar. The secondary circuit creates the connection to the air coolers at the work stations and removes heat. In another chamber of the pressure exchange system, the heated water stream of 30 bar is preloaded back to the high pressure of the shaft pipes and then returned to the surface, where the cooling circuit begins again.

Large flow meters of the MID-EX-GC or the MID-EX-GL and MIDEX series are used to monitor the warming/cooling output of the large refrigerating plants. These meters have a diameter of up to 400 mm and pressure levels up to PN500.